<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="js/jquery-1.3.1.js"></script>
</head>
<body>

</body>
</html>
<script type="text/javascript">
    //等待dom元素加载完毕.
    $(document).ready(function(){
        alert("Hello World!");
    });
</script>